The present invention relates to the field of the detection of one or several angular displacement parameters pertaining to a rotary member using an instrumented rolling bearing, that is to say one which has an information sensor block capable, in collaboration with an encoder element, of providing signals representing information relating to angular displacement, for example the displacement angle, the speed, the direction of rotation, of the rotary member.
Such instrumented rolling bearings are used in many applications, among which mention may more particularly be made of devices for controlling the orientation of the wheels of land vehicles such as touring cars, handling vehicles, civil engineering works vehicles, etc. Instrumented rolling bearings of this type are also used wherever there is a need, in a motor vehicle, to determine one or more parameters associated with the rotation of one of the wheels, of a member of the transmission or of the steering of the motor vehicle.
Instrumented rolling bearings generally comprise a sensor block mounted on the non-rotating ring of the bearing and an encoder ring mounted on the rotating ring and, during rotation, moving past a detection element comprising one or more sensors housed in the sensor block. The encoder ring may, for example, be of the multi-pole magnetic type. The sensor or sensors may be of the magnetically sensitive type as is the case, for example, of Hall-effect probes.
Use may also be made, in these instrumented rolling bearings, of a detection assembly comprising a sensor and an encoder of an optical type.
In general, the movement of the encoder past the detection element generates in the latter a signal representative of one or more parameters pertaining to the angular displacement of the encoder. From this, after appropriate processing of the signal, information relating to the angular displacement that is to be detected can be deduced, whether this be the angle of displacement, the angular speed, the direction of travel or any other parameter. For this purpose, the signal emitted is transmitted to a processing and operating unit by a set of connections generally comprising a cable leaving the sensor block of the instrumented rolling bearing via a wire terminal. The cable ends, for example, in a connector capable of transmitting the signal to the processing and operating unit.
In certain applications, absolute dependability and infallible detection of the desired parameter is demanded.
German patent application DE 195 10717 conceived of arranging two detection systems mounted on two separate rolling bearings.
Patent application EP 0 921 399 also conceived of arranging two identical detection elements on each side of the same rolling bearing, these elements each collaborating with its own encoder ring, each detection element transmitting its own information signals independently of one another to an electronic unit where the signal was processed and used.
While in this case an improvement in the dependability of the system is indeed achieved, since one of the detection elements is able, should the other malfunction, to palliate this failure, it is nonetheless found that there is a significant increase in the axial bulk of the instrumented rolling bearing thus equipped.
French patent application 2 558 223 describes the use, in an instrumented rolling bearing, of two sensors mounted on the same side of the rolling bearing on the same support, each sensor collaborating with its own encoder ring.
All these devices entail the use of two encoder rings, and this increases the cost price of the assembly accordingly.
The fact of using two separate encoders and independent sensor blocks also complicates the operations of indexing the encoder and the sensor with respect to a reference mark associated angularly with the encoder when the type of information detected or the application dictates such indexing.
Patent application EP-0 814 338 describes an orientation ring comprising, on the external frontal surface of the non-rotating ring, a magnetic synthetic strip bonded into a peripheral groove after cutting to the right length and acting as an encoder.
That document explains that a small region of groove not equipped with encoder may remain in that it is very difficult indeed to make the two ends of the magnetic strip meet. To avoid the resulting perturbations in the measurement, the document anticipates equipping the outer ring with two sensors inserted in a radial plane via through-holes made in the rotating ring.
Such a structure is complex because it entails providing two through-holes for the two sensors. In addition, the second sensor is intended to avoid the perturbations in the measurement resulting from the cut there is between the non-contiguous ends of the encoder strip. In the event of one of the encoders failing, the measurement remains perturbed.
The invention therefore proposes to eliminate these drawbacks by means of a detection device and an instrumented rolling bearing which ensure perfectly dependable detection of one or more parameters while at the same time being compact and inexpensive.
The device for detecting one or more angular displacement parameters pertaining to a rotary member, according to one embodiment of the invention, comprises an instrumented rolling bearing of the type provided with a non-rotating part comprising a non-rotating ring and a sensor block mounted on one face of the non-rotating ring, with a rotating part comprising a rotating ring and an encoder ring mounted facing the sensor block and with at least one row of rolling bodies arranged between two raceways of the non-rotating and rotating rings. Means for processing signals emitted by the sensor block are also provided. The single sensor block comprises at least two detection elements collaborating with the single encoder ring. Signals emitted independently by each detection element correspond to the same angular-displacement parameter, so as to provide the processing means with redundant information about said angular displacement parameter.
According to the invention, the single encoder is produced in the form of a continuous ring mounted in the rolling bearing in such a way as to ensure continuity of the signal.
The detection elements are advantageously mounted in a single sensor block arranged on just one side of the rolling bearing so as to reduce the overall bulk and make it simpler to manufacture.
In an advantageous embodiment, two detection elements are arranged diametrically opposed.
Each detection element preferably comprises at least one sensor.
Each detection element is preferably connected to the signal-processing means by an independent connection assembly.
The detection elements, thus being completely independent of one another, ensure a perfectly redundant system. If one of the detection elements becomes defective for one reason or another, another detection element is capable of fully taking its place.